FERMI

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FERMI Gamma-ray Space Telescope Sources in
the solar system observed by the Fermi Large Area
Telescope N.Giglietto (INFN and Politecnico of
Bari) on behalf of the FERMI LAT Collaboration
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Sources in Solar System

• Sources
• The Moon
• The Sun (quiet and/or flaring)
• The Earth
• Potential Sources
• Asteroids in different populations
• Main Asteroid Belt (MBAs)
• Jovian and Neptunian Trojans (Trojans)
• Kuiper Belt Objects (KBOs)
• Other planets
• Debris (lt few meter size, dust, grains) MBAs,
  Trojans, KBOs Oort Cloud

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Solar system objects observation interest

• Moon gamma ray emission depends by the nuclei CR
  flux intensity on surface
• Quiet solar gamma ray emission depends mainly by
  the electron flux interactions in the photosphere
  (IC) and the nuclei CR interactions inside the
  Sun
• Therefore the gamma ray emission studies are a
  sensible probe for CR fluxes in the solar system
• Gamma ray flux measurements during the entire
  solar cycle will be very important!

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Solar System observation capabilities with Fermi

• Solar Activity expected to peak around 2012
• Fermi will operate for nearly the entire duration
  of solar cycle 24

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Solar System observation capabilities with Fermi
(2)

• Fermi is the only satellite capable of making
  solar observations gt100 MeV
• Coordinated mesurements between LAT gamma-ray and
  GBM (10 keV-40 MeV)
• Comparison with RHESSI (1 keV 20 MeV)
• Comparison with energetic solar particle
  observations (ACE, STEREO, SOHO, WIND) and
  ground based experiments (Milagro) for flaring
  Sun alerts
• About ten high-energy flares expected during the
  FERMI operation period

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Emission mechanism

• ?-ray albedo due to CR interactions with
  surface material
• Moon rock (solid)
• Solar atmosphere (gaseous)
• Moon g-ray emission
• ?-rays produced by p0 decays produced in
  hadronic showers
• we expect lunar limb brighter then central disk
• ?-ray spectrum should be soft
• Similar emission mechanism for any solid object
  in solar system

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Sun second componentInverse Compton Scattering
e
e

• Inverse-Compton scattering of solar photons in
  the heliosphere by Galactic CR electrons the
  emission is predicted to be extended and the
  spectrum hard
• Electrons are isotropic
• Photons have a radial angular distribution

Moskalenko 06 OrlandoStrong08
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Fermi the Sun track in the sky
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Variability a 3 months look (north-south
galactic emisphere)
SUN path
Egt100MeV, poles view, 1day time interval,
extreme sensitivity to flux variations
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Data selection

• Data from Aug 2, 2008 until March 1, 2009
• Analysis in celestial relative coordinates
  (Moon and Sun centered data)
• SUN is moving about 1/day
• MOON is moving about 15/day
• E gt 100MeV
• Zenith angle lt 105 (to avoid the Earth limb)
• Galactic Plane Cut (gt30)
• Moon-Sun angular separation gt20
• ROI 10
• True/Fake source comparison

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Background estimation approach

• The fake source method
• A fake source follow the path of the real source
  but 30 degrees away (passes through the same
  areas on the sky but at different times)

N.Giglietto Vulcano workshop 2009
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The Moon first 7 months
Moon count map and projections in RA and DEC axes
centered on Moon position.Egt100MeV0.2deg/binga
ussian smothed
PRELIMINARY
PRELIMINARY
PRELIMINARY
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The Quiet Sun first 7 months
Sun count map and projections in RA and DEC axes
centered on Sun position.Egt100MeV0.2deg/bingaus
sian smothed
PRELIMINARY
N.Giglietto Vulcano workshop 2009
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Moon Spectra
- lower solar activity (upper solid line) -
hight solar activity (lower solid line)
Data EGRET

• limb (outer 5)
• center (inner 20)
• of the Moon disk

Moskalenko Porter07
Pion decay
Flux (Egt100MeV) (1.06 /- 0.20) x 10-6 ph cm-2
s-1(statistical 20 systematic error)
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The Sun spectra

• Sun Spectrum
• Red Point from Unfolding
• (statistical error only)
• Fit with a PL
• in the energy range
• 100MeV lt E lt 10GeV
• Spectral Index -2.25 /- 0.03

Flux(Egt100MeV) (4.6 /- 0.9) x 10-7 ph cm-2
s-1 (statistical 20 systematic error)
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Sun and Moon spectra a comparison
Moon and Sun Spectra Compared
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Sun the flux
P6V3 IRFs Flux (x 10-7 ph cm-2 s-1)
Fermi (Egt100MeV) 4.59 /- 0.89
Expected (total diskIC) (Moskalenko 06 OrlandoStrong 07) F(Egt100 MeV) 4.30 (_at_ solar min)
EGRET Flux not observed by EGRET (Thompson 97) (gt100MeV) 4.442.03 Reanalysis by OrlandoStrong08
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Conclusions

• During the first months of data taking Fermi has
  observed the quiet Sun and the Moon emission
• Preliminary Spectra and Fluxes has been reported
  for both sources
• Fermi will follow both the Moon and Sun emission
  during the entire solar cycle
• The Fermi preliminary results are consistent with
  predictions at solar minimum activity
• Fermi ready to detect high energy Solar Flares!

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Fermi/LAT performance (update in progress)
Energy Resolution 10 (5 off-axis) PSF
(68) at 100 MeV 5o PSF (68) at 1 GeV
0.6 PSF (68) at 10 GeV 0.1o Field Of View
2.4 sr Point Source sens. (gt100 MeV) 3x10-9 cm-2
s-1